Metallic sheet having rust-preventive organic coating thereon, process for the production thereof and treating fluid therefor

ABSTRACT

A metal plate having a rust preventive organic layer, said rust-preventive organic layer being a colloid or micelle of a slightly water soluble organic corrosion inhibitor as an organic layer mixed with and dispersed in a matrix resin, its production process and a treatment liquid in which it is processed.

TECHNICAL FIELD

The present invention relates to a metal plate having a rust-preventivelayer excellent in corrosion resistance and paint adhesion without usingany hexavalent chromium, its production process, and a treatment liquidin which it is processed.

BACKGROUND ART

In the past, metal plate was typically treated with chromate to form achromate layer in order to improve the corrosion resistance of coldrolled steel plate, zinc-plated steel plate, zinc alloy-plated steelplate, aluminum-plated steel plate, and so forth, used in automobiles,home appliances and construction material applications. Electrolyticchromate and coated chromate are examples of this chromate treatment. Inthe case of electrolytic chromate, for example, sheet steel was treatedby cathode electrolysis using a bath having as its main componentchromic acid to which were also added sulfuric acid, phosphoric acid,boric acid and various type of halogen and other ions. In addition, inthe case of coated chromate, due to the problem of elution of chromatefrom the chromate treated steel plate, a process is known, for example,in which the steel sheet is treated with a liquid containing inorganiccolloids and inorganic anions in addition to chromic acid in which aportion of the hexavalent chromium was reduced to trivalent chromium, inadvance, or to chromic acid having a specific ratio of hexavalentchromium to trivalent chromium. In addition, other methods that havebeen developed include a method in which the chromium is blocked bycompounding with an organic polymer, and a method in which the chromatelayer is additionally covered with an organic polymer.

Although chromate layer formed by electrolysis exhibit a low level ofelution of hexavalent chromium, their corrosion resistance cannot besaid to be adequate. In addition, the chromate layer is susceptible todamage during machining. Thus, there are certain problems with corrosionresistance after machining. In addition, in the case of chromate layerformed by coating, when used without modification after treatment,elution of a portion of the hexavalent chromium from the chromate layercannot be avoided. Resin-chromate has been developed to reduce thisdissolving of the chromate layer. However, deterioration of the resindue to the high oxidation effects of chromic acid cannot be avoided,thus preventing these chromate layers from having adequate coatingreliability in terms of industrial use. Although improved technologiescan be found, such as that which makes various adjustments in the resinstructure as disclosed in Japanese Unexamined Patent Publication No.5-230666, and that which attempts to achieve significant improvements inworkability and long-term coating stability involving the response ofthe chromate layer to a corrosive environment by regulating the form inwhich hexavalent chromium exists in the chromate layer as disclosed inJapanese Patent Application No. 7-149200, filed by the inventors of thepresent application, none of these can be said to be adequate from theviewpoint of completely inhibiting elution of hexavalent chromium.

In this way, in order to completely inhibit elution of hexavalentchromium, it is necessary to develop a rust-preventive layer havingfunctions identical to chromate layer containing hexavalent chromium ofthe prior art, but without using any hexavalent chromium whatsoever.

Until now, corrosion inhibitors have been developed for the purpose ofinhibiting corrosion of metal placed in a corrosive environment. Thisconsisted mainly of adding a trace amount of an inhibitor to a corrosivesolution, adsorbing onto the surface of the metal, and forming apassivating layer to decrease activation of the metal surface andinhibit ionized elution, and many such materials are known. Prominentexamples of inorganic compounds of these materials include hexavalentchromium salts, silica, phosphates and vanadates. Prominent examples oforganic compounds include carboxylic acids such as benzoates andazelates, and compounds containing —S— and —N— which easily formcomplexes with metal ions. However, since these compounds demonstrateeffects when trace amounts are added to a corrosive solution, thosecompounds that are able to form a layer on a metal surface and clearlydemonstrate long-term reliability are only chromate treatment andphosphate treatment including phosphate treatment. In the case oforganic compounds in particular, their reliability when used as singlelayer is extremely low.

For example, a paint composition and layer have been proposed that arecharacterized by containing 0.01 to 10 percent by weight (as solid) ofan organic corrosion inhibitor having a nitrogen atom in its molecule ina water-based paint as disclosed in Japanese Unexamined PatentPublication No. 4-318071 and Japanese Unexamined Patent Publication No.5-214273. Although water-soluble organic corrosion inhibitors andslightly water-soluble organic corrosion inhibitors proposed in theabove are both indicated in said patents, no clear distinctiontherebetween is made. In the case that the organic corrosion inhibitoris water-soluble, it elutes outside the layer when moisture enters in acorrosive environment, thereby preventing it from demonstrating adequatecorrosion resistance. In addition, in the case of a slightlywater-soluble organic corrosion inhibitor, it is typically extremelydifficult to disperse the inhibitor in water-based paints and, if simplymixed, causes aggregation in the paint or in the layer formed. Sincethis impairs the uniformity of the paint or layer, the stability of thepaint, as well as the resulting corrosion inhibitory effects, areinadequate. As a result of corrective measures still having not beentaken despite the existence of these problems, the corrosion resistancethat is obtained is inadequate.

In addition, in Japanese Unexamined Patent Opposition No. 7-97534,although a paint is proposed that contains 0.05 to 25 percent by weightof one or more types of alkynes, alkinols, amines or their salts, thiocompounds, heterocyclic compounds, polycarboxylic acid compounds ortheir salts, aromatic carboxylic acid compounds or their salts andlignin sulfonates or their salts, during application to metal plate, theformation of a chromate layer or zinc phosphate layer that serves as arust preventive layer is essential for pretreatment, and it cannot beexpected to demonstrate corrosion resistance when used as a singleorganic layer.

As has been described above, in the case of an single layer containingan organic corrosion inhibitor, when the organic corrosion inhibitor iswater-soluble, it elutes outside the layer when water enters in acorrosive environment, thereby preventing adequate corrosion resistance.In addition, when the organic corrosion inhibitor is hardlywater-soluble, it aggregates in the paint or layer thereby creatingproblems in the dispersion method or dispersion form. It is assumed thatthis type of organic corrosion inhibitor is unable to demonstrateadequate corrosion resistance because a site at which the organiccorrosion inhibitor is able to act efficiently cannot be obtained withinthe layer. Moreover, since the effect of organic corrosion inhibitorsconsists of inhibiting corrosion by forming a complex with metal ions,or in other words, anodic corrosion resistance which functions mainly byinhibition of metal ionization involving deposition at the interfaceafter forming a complex with eluted metal ions, and the pH region atwhich complex-forming functional groups required for complex formationare dissociated is unevenly distributed primarily in the neutral region,at low pH regions of the anode portion or in a rising pH environmentpresent during the early stages of corrosion, the effects of the organiccorrosion inhibitor are expected to be weak. In addition, aside fromtheir corrosion prevention ability, since the layer formation capabilityof these organic corrosion inhibitors onto a metal surface is generallyinferior to inorganic corrosion inhibitors and is considerably dependentupon environmental changes at the interface, it results in the problemof difficulty in maintaining stable adhesiveness. As a result, anorganic compound that offers both corrosion prevention and adherence toa certain extent must be selected, thus making further decreases incorrosion prevention unavoidable. The uses of these corrosion inhibitorsare limited to certain types of metals, and nearly all are limited touse as paint additives.

DISCLOSURE OF THE INVENTION

As a result of earnest research conducted by the inventors of thepresent invention to solve the problems of the above-mentioned organiccorrosion inhibitors or layer and to design a general-purpose chemicaltreatment layer to take the place of current chromate treatment in asystem that is completely free of hexavalent chromium, it was found thatthe problems could be solved by providing an organic corrosion inhibitorhaving effective corrosion resistance in the form of a fine colloid ormicelle and giving the ability to form a layer from resin. Accordingly,it became possible to dissolve the organic corrosion inhibitor anddemonstrate its function in a corrosion-inducing and corrosion-promotingenvironment (infiltration of moisture, change in pH, etc.), to therebygive the inhibitor a repair function that is selective for the corrosionsite. Moreover, the corrosion-resistance function of the inhibitor canbe enhanced by giving it the ability to prevent cathodic corrosion byusing a non-chromic inorganic colloid or electrically conductive polymercolloid, thereby making it possible to obtain a resin-based chemicaltreatment layer in which each material is able to efficientlydemonstrate its function.

The gist of the present invention is described below.

(1) A metal plate having a rust-preventive organic layer characterizedby a metal plate having a rust-preventive layer comprising a colloid ormicelle of a hardly water-soluble organic corrosion inhibitor dispersedin a matrix resin.

(2) A metal plate having a rust-preventive organic layer described in(1) above wherein the above-mentioned colloid or micelle has a averageparticle size of less than 1 μm.

(3) A metal plate having a rust-preventive organic layer described in(1) or (2) above wherein the above-mentioned colloid or micelle has aaverage particle size of 0.3 μm or less.

(4) A metal plate having a rust-preventive organic layer described in(1) through (3) above wherein the above-mentioned hardly water-solubleorganic corrosion inhibitor is one type or a mixture of two or moretypes of thioglycolate esters, mercaptocarboxylic acids, N-substitutedderivatives of 2,5-dimethylpyrrole, derivatives of 8-hydroxyquinoline,derivatives of triazinethiol, ester derivatives of gallic acid andelectrically conductive polymers.

(5) A metal plate having a rust-preventive organic layer described in(1) through (4) above wherein the above-mentioned matrix resin is anon-water-soluble copolymer resin composed of an organic polymercomprising one or a mixture of two or more types selected fromvinyl-based carboxylic acids, vinyl-based amines, vinyl-based alcoholsand vinyl-based phosphates having a high affinity with water, and one ora mixture of two or more types selected from vinyl-based compounds andolefins which have a low affinity with water and do not form a hydrate.

(6) A metal plate having a rust-preventive organic layer described in(1) through (4) above wherein the above-mentioned matrix resin isobtained from a non-water-soluble core-shell type emulsion resin havinga core phase of an organic polymer of one or a mixture of two or moretypes selected from vinyl-based monomers and olefins which do not form ahydrate, and a shell phase of an organic polymer of a monomer havinghigh affinity with water.

(7) A metal plate having a rust-preventive organic layer described in(1) through (4) above wherein the above-mentioned matrix resin is aresin made non-water-soluble by curing a water-soluble vinyl-based resinusing block isocyanate, amine or carboxylic acid.

(8) A metal plate having a rust-preventive organic layer described in(1) through (7) above wherein said rust-preventive organic film containsas additive in the above-mentioned matrix resin one or a mixture of twoor more types of inorganic colloids of Ca(OH)₂, CaCO₃, CaO, SiO₂,Zn₃(PO₄)₂, K₃PO₄, Ca₃ (PO₄)₂, LaPO₄, La(H₂PO₄)₃, CePO₄, Ce(H₂PO₄)₃,Ce(H₂PO₄)₄, CaSiO₃, ZrSiO₃, AlPO₄.nH₂O, TiO₂, ZrPO₄, ZnO, La₂O₃, CeO₂and Al₂O₃ as well as colloids of complex compound of these inorganicsubstances.

(9) A metal plate having a rust-preventive organic layer described in(1) through (8) above wherein said rust-preventive organic layercontains, as a passivating layer forming aid in the above-mentionedmatrix resin, one or a mixture of two or more types selected fromorthophosphoric acid, poly-phosphoric acids and meta-phosphoric acids.

(10) A metal plate having a rust-preventive organic layer described in(1) through (8) above wherein said rust-preventive organic layercontains, as a passivating layer forming aid in the above-mentionedmatrix resin, one or a mixture of two or more types selected fromorthophosphoric acid, poly-phosphoric acids and meta-phosphoric acids,and one type or a mixture of two or more types selected from ceriumsalts and lanthanum salts.

(11) A treatment liquid for forming a rust-preventive organic layer,characterized by comprising a layer forming resin dissolved or dispersedin an aqueous medium, and a colloid or micelle of a hardly water-solubleorganic corrosion inhibitor dispersed in said aqueous medium.

(12) A treatment liquid for forming a rust-preventive organic layerdescribed in (11) above wherein said colloid or micelle has a averageparticle size of less than 1 μm.

(13) A treatment liquid for forming a rust-preventive organic layerdescribed in (11) or (12) above wherein said colloid or micelle has aaverage particle size of 0.3 μm or less.

(14) A treatment liquid for forming a rust-preventive organic layerdescribed in (10) through (13) above wherein the above-mentioned hardlywater-soluble organic corrosion inhibitor is one type or a mixture oftwo or more types of thioglycolate esters, mercaptocarboxylic acids,N-substituted derivatives of 2,5-dimethylpyrrole, derivatives of8-hydroxyquinoline, derivatives of triazinethiol, ester derivatives ofgallic acid and electrically conductive polymers.

(15) A treatment liquid for forming a rust-preventive organic layerdescribed in (11) through (14) above wherein the above-mentioned layerforming resin is a non-water-soluble copolymer resin composed of anorganic polymer comprising one or a mixture of two or more typesselected from vinyl-based carboxylic acids, vinyl-based amines,vinyl-based alcohols and vinyl-based phosphates having a high affinitywith water, and one or a mixture of two or more types selected fromvinyl-based compounds and olefins which have a low affinity with waterand do not form a hydrate.

(16) A treatment liquid for forming a rust-preventive organic layerdescribed in (11) through (14) above wherein the above-mentioned layerforming resin is a non-water-soluble core-shell type emulsion resinhaving a core phase of an organic polymer of one or a mixture of two ormore types selected from vinyl-based monomers and olefins which do notform a hydrate, and a shell phase of an organic polymer of a monomerhaving high affinity with water.

(17) A treatment liquid for forming a rust-preventive organic layerdescribed in (11) through (14) above wherein the above-mentioned filmforming resin is a resin made non-water-soluble by curing awater-soluble vinyl-based resin using block isocyanate, amine orcarboxylic acid.

(18) A treatment liquid for forming a rust-preventive organic layerdescribed in (11) through (17) containing as additive one or a mixtureof two or more types of inorganic colloids of Ca(OH)₂, CaCO₃, CaO, SiO₂,Zn₃(PO₄)₂, K₃PO₄, Ca₃(PO₄)₂, LaPO₄, La(H₂PO₄)₃, CePO₄, Ce(H₂PO₄)₃,Ce(H₂PO₄)₄, CaSiO₃, ZrSiO₃, AlPO₄.nH₂O, TiO₂, ZrPO₄, ZnO, La₂O₃, CeO₂and A1 ₂O₃ as well as colloids of complex compound of these inorganicsubstances.

(19) A treatment liquid for forming a rust-preventive organic layerdescribed in (11) through (18) above containing as a passivating filmforming aid one or a mixture of two or more types selected fromorthophosphoric acid, poly-phosphoric acids and meta-phosphoric acids.

(20) A treatment liquid for forming a rust-preventive organic layerdescribed in (11) through (18) above containing as a passivating filmforming aid one or a mixture of two or more types selected fromorthophosphoric acid, poly-phosphoric acids and meta-phosphoric acids,and one type or a mixture of two or more types selected from ceriumsalts and lanthanum salts.

(21) A process for producing a metal plate having a rust-preventiveorganic layer, characterized by comprising applying to the surface of ametal plate a treatment liquid comprising a layer forming resindissolved or dispersed in an aqueous medium, and a colloid or micelle ofa hardly water-soluble organic corrosion inhibitor dispersed in saidaqueous medium, drying and, curing to form a rust-preventive organiclayer on the surface of said metal plate.

(22) A process for producing a metal plate having a rust-preventiveorganic layer described in (21) above wherein said colloid or micellehas a average particle size of less than 1 μm.

(23) A process for producing a metal plate having a rust-preventiveorganic layer described in (21) or (22) above wherein said colloid ormicelle has a average particle size of 0.3 μm or less.

(24) A process for producing a metal plate having a rust-preventiveorganic layer described in (21) through (23) above wherein theabove-mentioned hardly water-soluble organic corrosion inhibitor is onetype or a mixture of two or more types of thioglycolate esters,mercaptocarboxylic acids, N-substituted derivatives of2,5-dimethylpyrrole, derivatives of 8-hydroxyquinoline, derivatives oftriazinethiol, ester derivatives of gallic acid and electricallyconductive polymers.

(25) A process for producing a metal plate having a rust-preventiveorganic layer described in (21) through (24) above wherein theabove-mentioned layer forming resin is a non-water-soluble copolymerresin composed of an organic polymer comprising one or a mixture of twoor more types selected from vinyl-based carboxylic acids, vinyl-basedamines, vinyl-based alcohols and vinyl-based phosphates having a highaffinity with water, and one or a mixture of two or more types selectedfrom vinyl-based compounds and olefins which have a low affinity withwater and do not form a hydrate.

(26) A process for producing a metal plate having a rust-preventiveorganic layer described in (21) through (24) above wherein theabove-mentioned layer forming resin is a non-water-soluble core-shelltype emulsion resin having a core phase of an organic polymer of one ora mixture of two or more types selected from vinyl-based monomers andolefins which do not form a hydrate, and a shell phase of an organicpolymer of a monomer having high affinity with water.

(27) A process for producing a metal plate having a rust-preventiveorganic layer described in (21) through (24) above wherein theabove-mentioned layer forming resin is a resin made non-water-soluble bycuring a water-soluble vinyl-based resin using block isocyanate, amineor carboxylic acid.

(28) A process for producing a metal plate having a rust-preventiveorganic layer described in (21) through (27) wherein one or a mixture oftwo or more types of inorganic colloids of Ca(OH)₂, CaCO₃, CaO, SiO₂,Zn₃(PO₄)₂, K₃PO₄, Ca₃(PO₄)₂, LaPO₄, La(H₂PO₄)₃, CePO₄, Ce(H₂PO₄)₃,Ce(H₂PO₄)₄, CaSiO₃, ZrSiO₃, AlPO₄.nH₂O, TiO₂, ZrPO₄, ZnO, La₂O₃, CeO₂and Al₂O₃ as well as colloids of complex compound of these inorganicsubstances is contained as an additive.

(29) A process for producing a metal plate having a rust-preventiveorganic layer described in (21) through (28) above wherein one or amixture of two or more types selected from ortho-phosphoric acid,poly-phosphoric acids and meta-phosphoric acids is contained as apassivating layer forming aid.

(30) A process for producing a metal plate having a rust-preventiveorganic layer described in (21) through (28) above wherein one or amixture of two or more types selected from ortho-phosphoric acid,poly-phosphoric acids and meta-phosphoric acids, and one type or amixture of two or more types selected from cerium salts and lanthanumsalts is contained as a passivating layer forming aid.

(31) A process for producing a metal plate having a rust-preventiveorganic layer described in (21) through (30) above wherein a hardlywater-soluble organic corrosion inhibitor is dissolved in a solvent anddeposited and dispersed in the form of a fine colloid or micelle in anon-solvent and to which a passivated layer forming aid and inorganiccolloid are mixed and a dispersant as necessary is added to improvedispersivity and a matrix resin is added to form the above-mentionedtreatment liquid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of the polymer chain structure of acopolymer resin and telechelic resin.

FIG. 2 is a schematic drawing of a polymer chain aggregate (dispersionunit) resulting from aggregation of the polymer chains of a copolymerresin and telechelic resin in water.

FIG. 3 is a schematic drawing of the particle structure of a core-shelltype emulsion resin.

FIG. 4 is a cross-sectional conceptual drawing of a chemical treatmentlayer.

BEST MODE FOR CARRYING OUT THE INVENTION

The following provides a detailed explanation of the present inventionin accordance with the drawings.

As a result of dissolving a hardly water-soluble organic corrosioninhibitor in a solvent (protic polar solvent, etc.)and precipitating byplacing in water as a non-solvent to form a fine colloid or micelle, astrong interaction with resin is inhibited as well as, during entry ofmoisture in a corrosive environment following layer formation, a portionof the layer is dissolved to exhibit rust preventive effects. That is,the function of a gradually-released rust preventive is provided. Inaddition, the resulting rust preventive colloid or micelle is blendedwith an inorganic colloid having the ability to prevent cathodiccorrosion as well as a resin having excellent layer forming propertiesand adhesion with metal surfaces, to improve its corrosion inhibitoryfunction.

FIG. 4 is a cross-sectional conceptual drawing of a chemical treatmentlayer. As shown in FIG. 4, a chemical treatment layer 9 is formed on thesurface of metal plate 5, and a state is formed in the chemicaltreatment layer 9 wherein a colloid or micelle 6 of a hardlywater-soluble organic corrosion inhibitor and inorganic colloid 7 aredispersed in a matrix resin 8.

The size of the particles dispersed in the form of a colloid or micelleis said to generally be 1 μm or less. It is important in the presentinvention that, by using a resin-based chemically treating liquid inwhich an organic corrosion inhibitor is dispersed in the form of acolloid or micelle, the size of the particles of the treatment liquidbecomes substantially the particle size of the dispersed particles oforganic corrosion inhibitor in the resin-based chemically treated layer,and the organic corrosion inhibitor is finely dispersed in the resinlayer enabling it to efficiently exhibit corrosion preventive functions.Namely, the average particle size of the particles of the colloid ormicelle of the organic corrosion inhibitor dispersed in a resin-basedchemical treatment liquid or resin-based film (although secondaryparticles consisting of aggregations of primary particles are alsopresent in addition to primary particles, this refers to all particlespresent in the dispersed state) is less than 1 μm, preferably 0.7 μm orless, more preferably 0.3 μm or less and particularly preferably 0.15 μmor less.

It is preferable that the particle size of the colloid or micelle oforganic corrosion inhibitor be sufficiently small relative to the layerthickness. Even if the particle size is, for example, 1 μn or less, ifthe resin layer is too thin and the particles are not incorporated inthe resin matrix, the layer has numerous defects that result in impairedcorrosion resistance. As a general reference, it is preferable that theparticle size be no larger than half the layer thickness.

It is preferable that the matrix resin as claimed in the presentinvention be a non-water-soluble copolymer resin and telechelic resincomposed of a molecular skeleton that has a high affinity for water andadheres to the surface of metal materials by adsorption, hydrogen bondsand so forth, while the remainder is a molecular skeleton that has noaffinity for water, or a core-shell type emulsion resin composed of boththe above molecular skeletons, or a curing resin that is a water-solubleresin and is cured and made non-water-soluble by a crosslinking agentcontained in a paint during layer forming treatment. The structure ofthe non-water-soluble resin is shown in FIGS. 1, 2 and 3. FIG. 1 is aschematic drawing of the molecular chain structure of a copolymer resinand telechelic resin, FIG. 2 is a schematic drawing showing the polymerchain aggregate (dispersion unit) formed by aggregation of polymerchains of the above resin in water, and FIG. 3 is a schematic drawing ofthe particle structure of a core-shell type emulsion resin. In the caseof a resin using this type of water for the dispersant, when it is thenon-water-soluble resin, the molecule skeleton portion that has a highaffinity for water in an aqueous solvent (2 and 4 in the drawings)formsthe uppermost surface layer and covers the molecular skeleton portionthat has no affinity for water (1 and 3 in the drawings), which improvesthe mutual dispersivity of the resin particles and ensures stabledispersivity of the added colloid particles. In addition, in the case ofthe water-soluble resin, the molecular chain in an aqueous vehicle isstably dispersed in a completely hydrated state, and has gooddispersivity with colloid particles.

The reason for using a matrix resin having this type of structure isthat it serves as a skeleton that ensures stable dispersivity of colloidparticles and has stable properties as a treatment layer state, and hasthe properties of a gas barrier, ion permeation resistance, paintadhesiveness, finger print resistance, adhesion to metal surfaces andprocessability, and that the molecular skeleton portion having affinitywith water absorbs water during entry of moisture in a corrosiveenvironment to act as a site for dissolving of a corrosion inhibitorcolloid and exhibiting its function.

Thus, it is desirable to employ this type of resin structure. Examplesof the resin composition thereof, in the case of a non-water-solublecopolymer resin, include copolymer resins having for their monomersvinyl-based and olefin-based compounds. These are produced by varioustypes of polymerization methods such as solvent polymerization, bulkpolymerization, interfacial polymerization, suspension polymerizationand emulsion polymerization. The copolymer resin has the main skeletoncomposed of a polymer of a non-water-soluble, vinyl-based andolefin-based monomers and having, on both of its ends, an organicpolymer of vinyl-based carboxylic acid, vinyl-based amine, vinyl-basedsulfonic acid, vinyl-based alcohol, vinylphenol or vinyl-based phosphateand so forth having a high affinity with water and metal surfaces. Thetelechelic resin is obtained by introducing groups having affinity withwater and metal surfaces on both ends using a chain transfer agent inthe polymerization process of the non-water-soluble skeleton portion.The emulsion resin comprises a polymer of non-water-soluble vinyl-basedor olefin-based monomer as the core phase and a polymer of a monomerhaving a high affinity with metal surfaces as the shell phase.

Furthermore, in the case of these copolymer and core-shell type emulsionresins, although the weight ratio of the skeleton portion having a highaffinity for water and metal surface to the non-water-soluble skeletonportion is preferably high in order to ensure adhesion with metalsurface, if this weight ratio is excessively high, the coefficient ofwater absorption increases resulting in the occurrence of separation ofthe layer due to water swelling, which is undesirable. In addition, ifthe above-mentioned weight ratio is too low, adhesion with paint isimpaired which is also undesirable. Thus, it is desirable that thisweight ratio be adjusted to within a range from 3/100 to 3/2, andpreferably from 1/20 to 1/1. In addition, the above-mentioned resins arenot limited to these resins, but rather other resins used in waterdispersed paints may also be used without problem.

In addition, in the case of water-soluble resins, examples of resinsthat can be used include a polymer of a water-soluble vinyl-basedmonomer, a water-soluble resin composed of a polymer of water-solublevinyl-based monomers, or a water-soluble vinyl-based resin composed of acopolymer of a water-soluble vinyl-based monomer and a non-water-solublevinyl-based monomer, which becomes non- water-soluble due to theoccurrence of crosslinking between polymer molecular chains by a curingagent as a result of containing crosslinking functional groups (such asunsaturated bonds, —OH, —COOH and —NH₂) in its skeleton. Monomerscontaining polar groups can be used for the water-soluble vinyl-basedmonomer.

These polar groups refer to —COOH, —SO₃H, —P(O) (OH)₂, —OH and otherproton donating groups, or their salts, esters and —NH₂, —NHR, —NRR′(where R and R′ are alkyl groups or allyl groups) and other protonaccepting groups. Moreover, they also refer to quaternary ammoniumgroups having ionic bonds or amphoteric polar groups containing amixture of proton donating and accepting groups. A vinyl-based compoundinto which one or several types of these polar groups have beenintroduced can be used as the monomer. In addition, one or a mixture oftwo or more types of compounds selected from styrene, α-methylstyrene,vinyltoluene, chlorostyrene, alkyl(meth)acrylate esters andallyl(meth)acrylate esters can be used as the non-water-solublevinyl-based monomer.

Incidentally, introduction of this non-water-soluble vinyl polymerskeleton is performed to adjust the degree of crosslinking during curingby adjusting the total water solubility of the polymer. Although thereare no particular restrictions on the amount, it is preferable to adjustthe amount introduced so that the total solubility of the polymer inwater is at least 5% by weight and preferably at least 10% by weightunder normal pressure at 25° C. The polymer can be produced by using onetype or two or more types of these monomers. Moreover, the polymer maybe made water soluble by introducing the abovementioned functionalgroups into the non-water-soluble polymer. In addition, general-purposeamines, carboxylic acids and block isocyanates and so forth can be usedas the crosslinking agent, and the polymer can be made non-water-soluble by forming urethane bonds, acid amide bonds or ester bondsand so forth between polymer molecular chains.

A hardly water-soluble organic corrosion inhibitor is supplied to theabove-mentioned matrix resin in the form of a fine colloid or micelledispersed in water. Since this organic corrosion inhibitor has theability to adhere to metal surfaces and form a complex during elution ofmetal ions to capture those ions, it has the effect of inhibitingfurther progress of ionization. It is preferable that said corrosioninhibitor be a hardly water-soluble compound. This is because it givesthe ability to respond to a corrosive environment since it is expectedto demonstrate corrosion inhibitory effects by partially dissolvingusing the entry of moisture as a trigger. In addition, if said compoundis water-soluble, the compound does not exhibit its function as a resultof easily flowing out from the film during entry of moisture into thefilm. Alternatively, in the case of a paint system in which an organiccompound that serves as a good solvent of an organic corrosion inhibitoris used as the dispersant, the corrosion inhibitor becomes rigidly fixedin the resin film during film formation, which is undesirable since itscorrosion inhibitory effects decrease. Compounds that can be used forthis hardly water-soluble organic corrosion inhibitor include thosehaving at least two functional groups necessary for formation of metalcomplex bonds (═O, —NH₂, ═NH, ═N—, ═S, —OH, etc.) and those having afunctional group that allows the formation of covalent bonds with ametal surface (—OH, ═NH, —SH, —COH, —COOH, etc.).

Specific examples of these compounds include thioglycolate esters,mercaptocarboxylic acids, N-substituted derivatives of2,5-dimethylpyrrole, derivatives of 8-hydroxyquinoline, derivatives oftriazinethiol and ester derivatives of gallic acid. There are alsoelectrically conductive polymers used as organic materials that have adifferent corrosion prevention mechanism than the examples indicatedabove. These refer to single polymers having repeting units of widenedλ-electron conjugate bonds throughout the entire molecule, knownexamples of which include polyacetylene, polyaniline, polythiophene andpolypyrrole. These compounds can be given electrical conductivity byadding various types of electrolytes as dopants. In addition, in thecase of polyaniline, grades having improved solubility in water andelectrical conductivity by providing electrolytic functional groups(such as sulfone groups) within the molecular skeleton have beendeveloped and are commercially available. These compounds have lowsolubility in water and can be dispersed in water in the form of finecolloids.

Although the details of the corrosion prevention effects of theseelectrically conductive polymers is unknown, it is presumed that sincethese compounds are electrically conductive, they are able todemonstrate corrosion current rectifying effects and oxygen reductioninhibitory effects at the interface to act as a cathode corrosioninhibitor. Although various types of electrically conductive polymerscan be used, it is necessary that they have a certain degree ofsolubility in water in order to demonstrate corrosion prevention effectsby dissolving during entry of moisture in a corrosive environment.However, if water solubility is excessively high, outflow from the layeroccurs resulting in a decrease in function. Consequently, it ispreferable that they be adjusted to from 0.1 parts by weight to 10 partsby weight, and preferably from 0.1 parts by weight to 5 parts by weight,at normal pressure and 25° C.

Furthermore, although one type or a mixture of two or more types ofthese hardly water-soluble organic corrosion inhibitors are used, thetotal mixed amount is such that the amount of organic corrosioninhibitor added relative to the amount of matrix resin results in aratio of matrix resin to hardly water-soluble organic corrosioninhibitor (weight ratio) of from 100:1 to 1:2, preferably from 100:1 to2:1. If the amount of the added organic corrosion inhibitor is such thatthe weight ratio of matrix resin to refractory organic corrosioninhibitor is 1:2 or greater (not less than 2), the properties of theresin layer are significantly impaired. In addition, if the ratio is100:1 or less (not more than 1), corrosion prevention effects aresignificantly decreased. For this reason, it is preferable that theweight ratio be within the above-mentioned range.

Examples of these thioglycolate esters include aliphatic thioglycolateesters such as n-butyl thioglycolate and octyl thioglycolate, andaromatic thioglycolate esters such as phenyl thioglycolate and naphthylthioglycolate.

Mercaptocarboxylic acids are organic compounds containing at least onemercapto group and one carboxyl group each in their molecule andexamples include α-aliphatic mercaptocarboxylic acids such asα-mercaptolauric acid and α-mercaptocaproic acid along with their metalsalts, as well as heterocyclic mercaptocarboxylic acids such asmercaptonicotinic acid and 2-mercapto-1-acetotriazole along with theirmetal salts.

Examples of N-substituted forms of 2,5-dimethylpyrrole includeN-substituted forms such as N-butyl-2,5-dimethylpyrrole andN-phenyl-2,5-dimethylpyrrole along with their derivatives such asN-phenyl-3-formyl-2,5-dimethylpyrrole andN-phenyl-3,4-diformyl-2,5-dimethylpyrrole. Examples of derivatives of8-hydroxyquinoline include 8-hydroxyquinoline, their carboxylated andsulfonated derivatives along with their metal salts.

Examples of triazinethiol derivatives include tertiary amine-substitutedtriazinethiols such as 6-(N,N′-dibutyl)-amino-1,3,5-triazine-2,4-dithioland 6-(N,N′-octyl)-amino-1,3,5-triazine-2,4-dithiol.

Examples of ester derivatives of gallic acid include aliphatic estersand aromatic esters such as octyl gallate, stearyl gallate and phenylgallate.

Examples of electrically conductive polymers include polyacetylene,polyaniline, polypyrrole and polythiophene, their carboxyl groupderivatives, their sulfon group derivatives and their metal salts.

Non-chrome-based inorganic colloids are added to complement thecorrosion prevention effects of the above-mentioned organic corrosioninhibitor and enhance the ability to prevent cathodic corrosion.Specific examples of these include Ca(OH)₂, CaCO₃, CaO, SiO₂, Zn₃(PO₄)₂,K₃PO₄, Ca₃(PO₄)₂, LaPO₄, La(H₂PO₄)₃, CePO₄, Ce(H₂PO₄)₄, CaSiO₃, ZrSiO₃,AlPO₄.nH₂O, TiO₂, ZrPO₄, ZnO, La₂O₃, CeO₂ and Al₂O₃ as well as colloidsof complex compounds of these inorganic substances (complex oxides ofLa/Ce, complex phosphates of La/Ce, etc.). One type of a mixture of twoor more types of these can be used. If the amount of this inorganiccolloid added is a weight ratio of 1:2 or greater (not less than 2) interms of the ratio of matrix resin to inorganic colloid, the propertiesof the resin layer are significantly impaired. In addition, if the ratiois 50:1 or less (not more than 1), corrosion prevention effects are notdemonstrated. Consequently, it is preferable that the ratio of matrixresin to inorganic colloid (weight ratio) be from 50:1 to 1:2, andpreferably from 20:1 to 2:1.

In addition, examples of a passivating layer forming aid include onetype of a mixture of two or more types selected from ortho-phosphoricacid, poly-phosphoric acids and meta-phosphoric acids. One type or amixture of two or more types selected from cerium salts and lanthanumsalts can be added as necessary. Examples of trivalent cerium saltsinclude cerium acetate, cerium nitrate, cerium chloride, ceriumcarbonate, cerium oxalate and cerium sulfate. In addition, examples ofquaternary cerium salts include cerium sulfate, ammonium cerium sulfate,ammonium cerium nitrate, diammonium cerium sulfate and cerium hydroxide.Examples of lanthanum salts include lanthanum carbonate, lanthanumchloride, lanthanum nitrate, lanthanum oxalate, lanthanum sulfate andlanthanum acetate.

It is preferable that a cerium salt, a lanthanum salt, or a mixture withphosphate, be added so that the mixing ratio as the ratio of (number ofmoles of Ce and La) to (number of moles of P) be adjusted to be between2:1 and 1:100. Although it is possible to form a passivating layerduring coating even when the above-mentioned phosphate is added alone,as a result of adding phosphate in the presence of cerium salt orlanthanum salt in the above-mentioned ratio, the ability of phosphate toform a passivating layer can be maintained for a long time. If thephosphate ratio is less than 2:1, the ability to form a passivatinglayer during treatment layer formation is impaired, and if the ratio ofcerium or lanthanum is less than 1:100, the ability of phosphate to forma passivating layer can no longer be maintained for a long time.

With respect to the amounts added, if the blended weight ratio of matrixresin to passivating layer forming aid is 1:1 or greater (not more than1), the moisture absorption of the film increases resulting in problemsof coloring, decreased adhesion and so forth. In addition, if theabove-mentioned ratio is 30:1 or less (not more than 1), the ability toform a passivating layer is lost and there are no effects. Consequently,it is desirable that the ratio (weight ratio) of matrix resin topassivating layer forming aid is from 30:1 to 1:1, and preferably from20:1 to 2:1. In addition, if the concentration of matrix resin in thetreatment liquid is less than 50 g/l, the layer forming abilitydecreases which is undesirable since the layer lacks stability as a rustpreventive layer. Therefore, the concentration of matrix resin in thetreatment liquid should be adjusted to at least 50 g/l and preferably atleast 100 g/l.

Although there are no particular limitations on the metal plate that isthe subject of the present invention, examples of suitable metal plateinclude fused plated steel plates such as fused zinc-plated steel plate,fused zinc-iron alloy-plated steel plate, fused zinc-aluminum-magnesiumalloy-plated steel plate, fused aluminum-silicon alloy-plated steelplate and fused lead-tin alloy-plated steel plate, surface-treated steelplates such as electrically zinc-plated steel plate, electricallyzinc-nickel alloy-plated steel plate, electrically zinc-ironalloy-plated steel plate and electrically zinc-chrome alloy-plated steelplate, and cold-rolled steel plates, as well as zinc, aluminum and othermetal plates.

EXAMPLES

Matrix Resin

(1) Copolymer Resin

A copolymer of poly(methacryl acid, 2-hydroxyethylacrylate,2-hydroxyethylmethacrylate)poly(styrene, methylmethacrylate,n-butylmethacrylate, n-butylacrylate)-poly(methacrylate,2-hydroxyethylacrylate, 2-hydroxyethylmethacrylate) was prepared byliving anionic polymerization. Tetrahydrofuran (THF) was used for thesolvent, and s-BuLi was used for the catalyst. The reaction was carriedout successively using monomer charging ratios (weight ratio) ofmethylmethacrylate:2-hydroxyethylacrylate:2-hydroxyethylmethacrylate=3:4:3(1st stage of polymerization, resin terminal),styrene:methylmethacrylate:n-butylmethacrylate:nbutylacrylate=5:5:10:60(living polymerization, resin body), andmethylmethacrylate:2-hydroxyethylacrylate:2hydroxyethylmethacrylate=3:4:3(coupling polymerization, resin terminal). Furthermore, the reactiontemperature was 40-60° C., and the monomer charging amount/solvent ratiowas 2/100. Following completion of the reaction, the reaction solutionwas injected into petroleum ether and methanol to purify the resultingcopolymer resin. Moreover, for the purpose of dispersing in water, afterdissolving the copolymer resin in a polar solvent, the copolymer resinwas poured in water, formed into fine particles by intense stirring, andthen treated to remove the solvent and the concentration of the solidportion of the copolymer resin was adjusted.

(2) Telechelic Resin

An alcoholic hydroxyl group and carboxyl group were introduced onto theterminals of a copolymer of acrylic monomers by using mercaptopropionicacid, mercaptoethanol etc. as the chain transfer agent in an anionicpolymerization reaction process of poly(styrene, methylmethacrylate,n-butylmethacrylate, n-butylacrylate). 5 parts by weight of styrene, 5parts by weight of methylmethacrylate, 15 parts by weight ofn-butylmethacrylate and 75 parts by weight of n-butylacrylate werecharged in the form of monomers into 500 parts by weight of THF solvent,followed by the addition of 4,4′-azobis(4-cyanopentanic acid) aspolymerization initiator to conduct polymerization at 80° C. or lower.Purification and dispersion in water were performed using the sameprocedures as in the case of the copolymer resin.

(3) Core-Shell Type Emulsion Resin

A core-shell type resin consisting of styrene (5 parts by weight),methylmethacrylate (5 parts by weight), n-butylmethacrylate (10 parts byweight), n-butylacrylate (60 parts by weight), methacrylate (6 parts byweight), 2hydroxyethylacrylate (8 parts by weight) and2-hydroxyethylmethacrylate (6 parts by weight) was prepared by emulsionpolymerization. 40 parts by weight of the total of the above monomers interms of the charging ratios indicated in parentheses above were placedin 60 parts by weight of deionized water followed by the addition of 0.2parts by weight of sodium dodecylbenzenesulfate as emulsifier and 0.2parts by weight of ammonium persulfate as catalyst to prepare anemulsion resin while stirring intensely at 70° C. In addition, awater-based soap-free emulsion resin and so forth were suitably preparedaccording to the target properties of the film. In addition,commercially available water-based emulsion resins were also suitablypurchased and used.

(4) Water-Soluble Resin and its Cured Form

15 parts by weight of 2-hydroxyethylacrylate were placed in 85 parts byweight of deionized water followed by addition of 0.3 parts by weight ofammonium persulfate as catalyst to prepare a water-based resin at 40° C.In addition, copolymers of 2-hydroxyethylacrylate and acrylic acid werealso prepared using the same procedure. In addition, a copolymer of awater-soluble monomer and non-water-soluble monomer such as2-hydroxyethylacrylate and n-butylacrylate were suitably prepared in anorganic solvent using the method described in the example of preparationof a copolymer resin, and used after purifying and dissolving in water.Dicarboxylic acids such as adipic acid and terephthalic acid, diaminessuch as ethylenediamine, and isocyanates such as polyoxyethylenediisocyanate were used as crosslinking agents for the curing agent.

(5) SBR Latex

A commercially available styrene butadiene rubber latex containingcarboxyl groups (Japan Synthetic Rubber) was used.

(A) 2-40 parts by weight of butyl thioglycolate, octyl thioglycolate,stearyl thioglycolate, α-mercaptolauric acid, α-mercaptocaproic acid,8-hydroxyquinoline, 6-(N,N′-dibutyl)-amino-1,3,5-triazine-2,4-dithioland lauryl gallate were each added separately to 100 parts by weight ofalcohol (ethanol, isopropyl alcohol, etc.) and after completelydissolving, dropped into deionized water to prepare colloids or micellesof these organic corrosion inhibitors.

(B) In the above-mentioned corrosion inhibitor colloid preparationprocess, an alcohol solution of the corrosion inhibitor was dropped intoa silica gel solution (Nissan Chemical, solid portion: 20% by weight, pH2) or a cerium oxide sol solution (Johnson Matthey, 0.1 M/l of aqueousnitric acid, solid portion: 50 g/l, dispersed in nonionic surfaceactivator) to form a colloid or micelle of organic corrosion inhibitorin an aqueous solution of dispersed inorganic colloid.

(C) N-phenyl-3-formyl-2,5-dimethylpyrrole was synthesized using theKnorr-Pall condensation reaction of 2,5-hexanedione and aniline, andafter dissolving the obtained compound to 20% by weight in aqueoussulfuric acid at pH 1 by taking advantage of the solubility of saidcompound in acidic aqueous solutions, aqueous sodium hydroxide solutionwas dropped in to form a colloid in the pH range of 4 to 7.

(D) In the water-dispersed colloid preparation process of saidN-phenyl-3-formyl-2,5-dimethylpyrrole,N-phenyl-3-formyl-2,5-dimethylpyrrole was dissolved to 20% by weight inthe silica gel solution (Nissan Chemical, solid portion: 20% by weight,pH 2) or cerium oxide sol solution (Johnson Matthey, 0.1 M/l of aqueousnitric acid, solid portion: 50 g/l, dispersed in nonionic surfaceactivator) described in (B) as a acidic aqueous solution and aqueoussodium hydroxide solution was then dropped in to form a colloid in thepH range of 4 to 7.

(E) A 1% by weight aqueous solution of polyaniline as electricallyconductive polymer containing barium sulfate as dopant was purchased(Japan Carlit), and a water-dispersed colloid of electrically conductivepolymer was prepared by concentrating by a factor of 15 by evaporation.

Treatment Liquid Preparation Method

The above-mentioned water-dispersed colloid or micelle of a hardlywater-soluble organic corrosion inhibitor, matrix resin,non-chrome-based inorganic colloid, along with cerium chloride (CeCl₃),lanthanum nitrate (La(NO₃)₃) and/or phosphoric acid as passivating layerforming aid were blended and formed into a bath. The total amount ofhardly water-soluble organic corrosion inhibitor was fixed at 40 g/l,the total amount of inorganic colloid at 40 g/l, resin at 100 g/l andphosphoric acid at 20 g/l. In addition, a liquid containing gallic acidas water-soluble organic corrosion inhibitor was also prepared forcomparison purposes. The compositions of these treatment liquids areshown in Tables 1 and 2.

Treatment Layer Forming Method

The above-mentioned treatment liquids were coated onto steel plate,dried and cured to form a treatment layer. The steel plates usedconsisted of GI (fused galvanized steel plate, plated amount: 90 g/m²),EG (electrically galvanized steel plate, plated amount: 20 g/m²), SZ(fused zinc-aluminum alloy-plated steel plate, plated amount: 90 g/m²,Zn/Al=95.2/4.8), AL (fused aluminum-silicon alloy-plated steel plate,plated amount: 120 g/m², Al/Si=90/10) and CR (cold rolled steel plate).Furthermore, a treatment liquid was prepared in the form of a chromatetreatment liquid for the purpose of comparing with the chromate treatedsteel plates that contained 30 g/l as CrO₃ of partially starch-reducedchromic acid, 40 g/l of SiO₂ and 20 g/l of ortho-phosphoric acid. Thistreatment liquid was similarly coated onto a steel plate, dried andcured to form a treatment layer.

Furthermore, coating was performed using a bar coater with a layerthickness of about 1 μm after drying, and the coated layer was dried for30 seconds at a plate temperature of 200° C. and cured.

TABLE 1 Corrosion Inorganic Passivating Treatment Matrix Resin InhibitorColloid Layer Liquid (100 g/l) (40 g/l) (40 g/l) Forming Aid Remarks 1Copolymer resin *TGB: 30 g/l *SiO₂: 38 g/l Ortho-phoshoric Examples *ML:10 g/l *CeO₂:  2 g/l acid 20 g/l 2 Telechelic resin *8-HQ: 35 g/l *SiO₂:40 g/l Ortho-phosphoric (terminal OH group) *PA  5 g/l acid 20 g/l 3Core-shell emulsion *PFP: 40 g/l SiO₂: 38 g/l Ortho-phosphoric resinCeO₂:  2 g/l acid 20 g/l 4 Crosslinking resin *PFP: 35 g/l SiO₂: 40 g/lOrtho-phosphoric *2-hydroxyethyl *PA:  5 g/l acid 20 g/l acrylate (90parts by weight) *Isocyanate (10 parts by weight) 5 Copolymer resin TGB:30 g/l SiO₂: 38 g/l Ortho-phosphoric TDT: 10 g/l CeO₂:  2 g/l acid 20g/l 6 Telechelic resin TGS: 30 g/l SiO₂: 38 g/l Ortho-phosphoric(terminal COOH MC: 10 g/l CeO₂:  2 g/l acid 20 g/l group) 7 Core-shellemulsion *GL: 40 g/l SiO₂: 38 g/l Ortho-phosphoric resin CeO₂:  2 g/lacid 20 g/l 8 Crosslinking resin PFP: 35 g/l SiO₂: 38 g/lOrtho-phosphoric *2-hydroxyethyl PA:  5 g/l CeO₂:  2 g/l acid 20 g/lacrylate (80 parts by weight) *Acrylic acid (10 parts by weight)*Isocyanate (10 parts by weight) 9 Core-shell emulsion Gallic acid:SiO₂: 40 g/l Ortho-phosphoric Comparative resin 40 g/l acid 20 g/lExamples (water-soluble) 10    — Reduced chromic SiO₂: 40 g/lOrtho-phosphoric acid 30 g/l as acid 20 g/l CrO₃) TGB:Butylthioglycolate TGO: Octylthioglycolate TGS: Stearylthioglycolate ML:α-mercaptolauric acid MC: α-mercaptocaproic acid 8-HQ:8-hydroxyquinoline TDT: 6-(N,N′)-amino-1,3,5-triazine-2,4-dithiol GL:Lauryl gallate PFP: N-phenyl-3-formyl-2,5-dimethylpyrrole PA:Polyaniline

TABLE 2 Passivating Layer Treat- Corrosion Inorganic Forming Aid mentMatrix Resin Inhibitor Colloid Phosphoric Liquid (100 g/l) (40 g/l) (40g/l) Metal Salt Acid Remarks 11 Copolymer resin *TGB: 30 g/l *SiO₂: 40g/l *CeCl₃:  5 g/l Ortho- Examples *ML: 10 g/l *La(NO₃)₃:  5 g/lphosphoric acid: 20 g/l 12 Telechelic resin *8-HQ: 35 g/l *SiO₂: 40 g/l*LaCl₃: 10 g/l Ortho- (terminal OH *PA:  5 g/l phosphoric group) acid:20 g/l 13 Core-shell *PFP: 40 g/l *SiO₂: 40 g/l *Ce(NO₃)₃: 10 g/l Ortho-emulsion resin phosphoric acid: 20 g/l 14 Crosslinking *PFP: 35 g/l*SiO₂: 40 g/l *CeCl₃:  5 g/l Ortho- resin *PA:  5 g/l *La(NO₃)₃:  5 g/lphosphoric *2-hydroxyethyl acid: 20 g/l acrylate (90 parts by weight)*Isocyanate (10 parts by weight) 15 SBR latex *ML: 40 g/l *SiO₂: 40 g/l*Ce(NO₃)₃:  5 g/l Ortho- *LaCl₃:  5 g/l phosphoric acid: 20 g/l

Treatment Layer Performance Evaluation Method

(a) Flat plate corrosion resistance was evaluated in terms of the ratioof the surface area on which rust formed after spraying the sample with5% salt water at 35° C. Furthermore, the spraying times were 10 days forGI, EG and SZ, and 15 days for AL. All samples were measured for theincidence of white rust with the exception of CR which was measured forthe incidence of red rust after 5 days.

Scoring

⊚: No formation of rust

∘: Rust incidence of less than 5%

Δ: Rust incidence of greater than 5% but less than 20%

×: Rust incidence of greater than 20%

(b) Paint adhesion was evaluated in terms of the ratio of surface fromwhich paint peeled in the cross-cut adhesion test (tape peeling from apattern of 10 squares×10 squares measuring 1 mm on a side) following theapplication of melamine-alkyd paint onto the sample at a thickness of 20μm, drying and immersion in boiling water for 30 minutes.

Scoring

⊚: No peeling

∘: Peeling ratio less than 5%

Δ: Peeling ratio of greater than 5% but less than 20%

×: Peeling ratio of greater than 20%

(c) Resistance to fingerprints was evaluated in terms of the colordifference (ΔE) before and after application of Vaseline on the sample.The smaller the color difference, the better the resistance tofingerprints.

⊚: ΔE<0.5

∘: 0.5<ΔE<1.0

Δ: 1.0<ΔE<3.0

×: 3.0<ΔE

(d) The layer on a steel plate was cut with a microtome and stained withtungsten phosphate, osmic acid, ruthenic acid and so forth followed byobservation of the cross-sectional structure of the layer by TEM todetermine the average particle size of the organic corrosion inhibitor.

The results of these performance evaluation tests are shown in Table 3.Furthermore, when the cross-sections of layers, which were formed byadding organic corrosion inhibitors in the same compositions astreatment liquids 1 through 10 without forming a colloid or micelleusing a mixture of organic corrosion inhibitors forcibly mixed with ahand mixer for the treatment liquid, coating onto EG, drying and curing,were observed by TEM, the average particle size of the organic corrosioninhibitor was larger than 1 μm in all cases. Although similar evaluationtests were also performed on these layers, they all fell below theperformance level of the present invention. Evaluation of corrosionresistance in particular resulted in an incidence of white rust ofgreater than 20% following spraying of salt water for 10 days.

As is clear from Table 3, treatment layers in which the hardlywater-soluble organic corrosion inhibitor was dispersed in the form of acolloid or micelle according to the present invention demonstratedcorrosion resistance and paint adhesion comparable to chromate layer,while demonstrating better resistance to fingerprints. Thus, the presentinvention is able to demonstrate excellent effects as a chemicallytreated layer that is completely free of hexavalent chromium andcompatible with the environment.

TABLE 3 Average particle size of Treat- organic Flat plate Paint Finger-ment Steel corrosion corrosion ad- print Re- Liquid Plate inhibitorresistance hesion resistance marks 1 EG 0.43 μm ⊚ ⊚ ⊚ Exam- GI ◯ ⊚ ⊚ples 2 EG, SZ, 0.17 μm ⊚ ⊚ ⊚ AL GI ⊚ ◯ ⊚ 3 EG, SZ 0.22 μm ⊚ ⊚ ⊚ GI, AL ⊚◯ ⊚ 4 EG 0.28 μm ⊚ ⊚ ⊚ GI ⊚ ◯ ⊚ 5 EG 0.52 μm ⊚ ◯ ⊚ GI ◯ ⊚ ⊚ 6 EG, AL0.75 μm ◯ ◯ ⊚ SZ, GI ⊚ ⊚ ⊚ 7 EG, GI 0.82 μm ◯ ◯ ⊚ CR ⊚ ⊚ ⊚ 8 AL 0.11 μm⊚ ⊚ ⊚ CR ⊚ ⊚ ⊚ 9 EG, GI — Δ Δ ◯ Comp. CR Δ Δ ◯ Exam- 10  EG — ◯ Δ Δ plesGI ◯ Δ Δ 11  EG, SZ, 0.20 μm ⊚ ⊚ ⊚ Exam- AL ples GI ◯ ⊚ ⊚ 12  EG, SZ,0.17 μm ⊚ ⊚ ⊚ AL GI ⊚ ◯ ⊚ 13  EG, SZ, 0.13 μm ⊚ ⊚ ⊚ AL, GI CR ⊚ ⊚ ⊚ 14 EG, GI 0.46 μm ◯ ⊚ ⊚ CR ⊚ ⊚ ⊚ 15  SZ, AL, 0.44 μm ⊚ ⊚ ⊚ GI EG ◯ ⊚ ⊚

As has been described above, the resin layer obtained by providing thehardly water-soluble organic corrosion inhibitor in the form of acolloid or micelle and mixing and dispersing with a resin havingexcellent layer forming properties, an inorganic colloid having theability to prevent cathodic corrosion, and a passivating layer formingaid in accordance with the present invention, has the function of agradually-released chemical that exhibits rust preventive effects as aresult of the organic corrosion inhibitor colloid or micelle partiallydissolved when triggered by the entry of moisture in a corrosiveenvironment, thereby enabling it to demonstrate selective repair effectson corroded portions. Consequently, this treatment layer exhibitsperformance equal to or better than a layer containing hexavalentchromium and demonstrates extremely superior effects while also beingenvironmentally friendly.

Industrial Applicability

Metal plates having the rust preventing organic layer of the presentinvention can be used as cold rolled steel plate, zinc-plated steelplate and other types of metal plates used in automobiles, homeappliances and construction material applications.

What is claimed is:
 1. A metal plate having a rust-preventive organiclayer wherein the rust-preventive layer comprises a colloid or micelleof a non-water soluble organic corrosion inhibitor dispersed in a matrixresin, wherein said colloid or miscelle has an average particle size ofless than 1 μm.
 2. A metal plate having a rust-preventive organic layeras set forth in claim 1 wherein said colloid or micelle has a averageparticle size of 0.3 μm or less.
 3. A metal plate having arust-preventive organic layer as set forth in claim 1 wherein saidnon-water soluble organic corrosion inhibitor is one type or a mixtureof two or more types of thioglycolate esters, mercaptocarboxylic acids,organic compounds having an N-substituted 2,5-dimethylpyrrole structurein the molecule, organic compounds having an 8-hydroxyquinolinestructure in the molecule, organic compounds having a triazinethiolstructure in the molecule, gallic acid esters, or electricallyconductive polymers.
 4. A metal plate having a rust-preventive organiclayer as set forth in claim 1 wherein said matrix resin is anon-water-soluble copolymer resin composed of an organic polymercomprising one or a mixture of two or more types selected from the groupconsisting of vinyl-based carboxylic acids, vinyl-based amines,vinyl-based alcohols, and vinyl-based phosphates having an affinity withwater, and one or a mixture of two or more types selected from the groupconsisting of vinyl-based compounds and olefins which do not form ahydrate.
 5. A metal plate having a rust-preventive organic layer as setforth in claim 1 wherein said matrix resin is obtained from anon-water-soluble core-shell type emulsion resin comprising a core phaseof an organic polymer of one or a mixture of two or more types selectedfrom the group consisting of vinyl-based monomers and olefins which donot form a hydrate, and a shell phase of an organic polymer of a monomerhaving an affinity with water.
 6. A metal plate having a rust-preventiveorganic layer as set forth in claim 1 wherein said matrix resin is aresin made non-water-soluble by curing a water-soluble vinyl-based resinusing block isocyanate, amine, or carbolic acid.
 7. A metal plate havinga rust-preventive organic layer as set forth in claim 1 wherein saidrust-preventive organic film contains, as additive in the said matrixresin, one or a mixture of two or more types of inorganic colloids ofCa(OH)₂, CaCO₃, CaO, SiO₂, Zn₃(PO₄)₂, K₃PO₄, Ca₃(PO₄)₂, LaPO₄,La(H₂PO₄)₃, CePO₄, Ce(H₂PO₄)₃, Ce(H₂PO₄)₄, CaSiO₃, ZrSiO₃, AlPO₄.nH₂O,TiO₂, ZrPO₄, ZnO, La₂O₃, CeO₂, or Al₂O₃ as well as colloids of complexcompound of these inorganic substances.
 8. A metal plate having arust-preventive organic layer as set forth in claim 1 wherein saidrust-preventive organic layer contains, as a passivating film formingaid in said matrix resin, one or a mixture of two or more types selectedfrom the group consisting of ortho-phosphoric acid, poly-phosphoricacids, and meta-phosphoric acids.
 9. A metal plate having arust-preventive organic layer as set forth in claim 1 wherein saidrust-preventive organic layer contains, as a passivating layer formingaid in said matrix resin, one or a mixture of two or more types selectedfrom the group consisting of ortho-phosphoric acid, poly-phosphoricacids, and meta-phosphoric acids, and one type or a mixture of two ormore types selected from the group consisting of cerium salts andlanthanum salts.
 10. A treatment liquid for forming a rust-preventiveorganic layer, characterized by comprising a layer forming resindissolved or dispersed in an aqueous medium, and a colloid or micelle ofa non-water-soluble organic corrosion inhibitor dispersed in saidaqueous medium, wherein said colloid or micelle has an average particesize of less than 1 μm.
 11. A treatment liquid for forming arust-preventive organic layer as set forth in claim 10 wherein saidcolloid or micelle has a average particle size of 0.3 μm or less.
 12. Atreatment liquid for forming a rust-preventive organic layer as setforth in claim 10 wherein said non-water-soluble organic corrosioninhibitor is one type or a mixture of two or more types of thioglycolateesters, mercaptocarboxylic acids, organic compounds having anN-substituted 2,5-dimethylpyrrole structure in the molecule, organiccompounds having an 8-hydroxyquinoline structure in the molecule,organic compounds having a triazinethiol structure in the molecule,gallic acid esters, or electrically conductive polymers.
 13. A treatmentliquid for forming a rust-preventive organic layer as set forth in claim10 wherein said layer forming resin is a non-water-soluble copolymerresin composed of an organic polymer comprising one or a mixture of twoor more types selected from the group consisting of vinyl-basedcarboxylic acids, vinyl-based amines, vinyl-based alcohols, andvinyl-based phosphates having an affinity with water, and one or amixture of two or more types selected from the group consisting ofvinyl-based compounds and olefins which do not form a hydrate.
 14. Atreatment liquid for forming a rust-preventive organic layer as setforth in claim 10 wherein said layer forming resin is anon-water-soluble core-shell type emulsion resin comprising a core phaseof an organic polymer of one or a mixture of two or more types selectedfrom the group consisting of vinyl-based monomers and olefins which donot form a hydrate, and a shell phase of an organic polymer of a monomerhaving an affinity with water.
 15. A treatment liquid for forming arust-preventive organic layer as set forth in claim 10 wherein saidlayer forming resin is a resin made non-water-soluble by curing awater-soluble vinyl-based resin using block isocyanate, amine, orcarboxylic acid.
 16. A treatment liquid for forming a rust-preventiveorganic layer as set forth in claim 10 containing, as an additive, oneor a mixture of two or more types of inorganic colloids of Ca(OH)₂,CaCO₃, CaO, SiO₂, Zn₃(PO₄)₂, K₃PO₄, Ca₃(PO₄)₂, LaPO₄, La(H₂PO₄)₃, CePO₄,Ce(H₂PO₄)₃, Ce(H₂PO₄)₄, CaSiO₃, ZrSiO₃, AlPO₄.nH₂O, TiO₂, ZrPO₄, ZnO,La₂O₃, CeO₂, or Al₂O₃ as well as colloids of complex compound of theseinorganic substances.
 17. A treatment liquid for forming arust-preventive organic layer as set forth in claim 10 containing, as apassivating layer forming aid, one or a mixture of two or more typesselected from the group consisting of ortho-phosphoric acid,poly-phosphoric acids, and meta-phosphoric acids.
 18. A treatment liquidfor forming a rust-preventive organic layer as set forth in claim 10containing, as a passivating layer forming aid, one or a mixture of twoor more types selected from the group consisting of ortho-phosphoricacid, poly-phosphoric acids, and meta-phosphoric acids, and one type ora mixture of two or more types selected from the group consisting ofcerium salts and lanthanum salts.
 19. A process for producing a metalplate having a rust-preventive organic layer, characterized bycomprising applying to the surface of a metal plate a treatment liquidcomprising a layer forming resin dissolved or dispersed in an aqueousmedium, and a colloid or micelle of a non-water-soluble organiccorrosion inhibitor having an average particle size of less than 1 μmdispersed in said aqueous medium and drying and curing the treatmentliquid to form a rust-preventive organic layer on the surface of saidmetal plate.
 20. A process for producing a metal plate having arust-preventive organic layer as set forth in claim 19 wherein saidcolloid or micelle has a average particle size of 0.3 μm or less.
 21. Aprocess for producing a metal plate having a rust-preventive organiclayer as set forth in claim 19 wherein said substantiallynon-water-soluble organic corrosion inhibitor is one type or a mixtureof two or more types of thioglycolate esters, mercaptocarboxylic acids,organic compounds having an N-substituted 2,5-dimethylpyrrole structurein the molecule, organic compounds having an 8-hydroxyquinolinestructure in the molecule, organic compounds having a triazinethiolstructure of the molecule, gallic acid esters, or electricallyconductive polymers.
 22. A process for producing a metal plate having arust-preventive organic layer as set forth in claim 19 wherein saidlayer forming resin is a non-water-soluble copolymer resin composed ofan organic polymer comprising one or a mixture of two or more typesselected from the group consisting of vinyl-based carboxylic acids,vinyl-based amines, vinyl-based alcohols, and vinyl-based phosphateshaving an affinity with water, and one or a mixture of two or more typesselected from the group consisting of vinyl-based compounds and olefinswhich do not form a hydrate.
 23. A process for producing a metal platehaving a rust-preventive organic layer as set forth in claim 19 whereinsaid layer forming resin is a non-water-soluble core-shell type emulsionresin comprising a core phase of an organic polymer of one or a mixtureof two or more types selected from the group consisting of vinyl-basedmonomers and olefins which do not form a hydrate, and a shell phase ofan organic polymer of a monomer having an affinity with water.
 24. Aprocess for producing a metal plate having a rust-preventive organiclayer as set forth in claim 19 wherein said layer forming resin is aresin made non-water-soluble by curing a water-soluble vinyl-based resinusing block isocyanate, amine, or carboxylic acid.
 25. A process forproducing a metal plate hav g a rust-preventive organic layer as setforth in claim 19 wherein one or a mixture of two or more types ofinorganic colloids of Ca(OH)₂, CaCO₃, CaO, SiO₂, Zn₃(PO₄)₂, K₃PO₄,Ca₃(PO₄)₂, LaPO₄, La(H₂PO₄)₃, CePO₄, Ce(H₂PO₄)₃, Ce(H₂PO₄)₄, CaSiO₃,ZrSiO₃, AlPO₄.nH₂O, TiO₂, ZrPO₄, ZnO, La₂O₃, CeO₂, or Al₂O₃ as well ascomplex colloids of compound of these inorganic substances is containedas an additive.
 26. A process for producing a metal plate having arust-preventive organic layer as set forth in claim 19 wherein one or amixture of two or more types selected from the group consisting ofortho-phosphoric acid, poly-phosphoric acids and meta-phosphoric acidsis contained as a passivating layer forming aid.
 27. A process forproducing a metal plate having a rust-preventive organic layer as setforth in claim 19 wherein one or a mixture of two or more types selectedfrom the group consisting of ortho-phosphoric acid, poly-phosphoricacids, and meta-phosphoric acids, and one type or a mixture of two ormore types selected from the group consisting of cerium salts andlanthanum salts is contained as a passivating layer forming aid.
 28. Aprocess for producing a metal plate having a rust-preventive organiclayer as set forth in claim 19, wherein a non-water-solublewater-soluble organic corrosion inhibitor is dissolved in a solvent anddeposited and dispersed in the form of a fine colloid or micelle in anon-solvent, to which a passivated layer forming aid and inorganiccolloid are mixed and a dispersant as necessary is added to improvedispersivity, and a matrix resin is added to form said treatment liquid.